Catalyst demetallization and process for using demetallized catalyst

ABSTRACT

An improved catalyst demetallization process involves chlorinating the metal contaminated catalyst at elevated temperatures and contacting the chlorinated catalyst with a liquid aqueous composition to produce a demetallized catalyst. Improved catalytic activity is obtained utilizing a catalyst comprising at least one crystalline material capable of promoting the hydrocarbon conversion, and cooling the chlorinated catalyst prior to contact with the liquid aqueous composition. An improved hydrocarbon conversion process is also disclosed.

The present invention relates to improved demetallization of catalystwhich is contaminated by one or more metals in hydrocarbon conversionservice. More particularly, the invention relates to such an improvedcatalyst demetallization process which involves at least partiallychlorinating the catalyst.

Catalytically promoted processes for the chemical conversion ofhydrocarbons include cracking, hydrocracking, reforming,hydrodenitrogenation, hydrodesulfurization, etc. Such reactionsgenerally are performed at elevated temperatures, for example, about 300degrees F. to 1200 degrees F., more often about 600 degrees F. to about1000 degrees F. Feedstocks to these processes comprise normally liquidand solid hydrocarbons which, at the temperature of the conversionreaction, are generally in the fluid, i.e., liquid or vapor state, andthe products of the conversion usually are more valuable, lower boilingmaterials.

In particular, cracking of hydrocarbon feedstocks to producehydrocarbons of preferred octane rating boiling in the gasoline range iswidely practiced and uses a variety of solid catalysts comprising atleast one of certain synthetic crystalline materials to give morevaluable end products. Cracking is ordinarily effected to producegasoline as the most valuable product and is generally conducted attemperatures of about 750 degrees F. to about 1100 degrees F.,preferably about 850 degrees F. to about 950 degrees F., at pressures upto about 2000 psig., preferably about atmospheric to about 100 psig. andwithout substantial addition of free hydrogen to the system. Incracking, the feedstock is usually a petroleum hydrocarbon fraction suchas straight run or recycle gas oils or other normally liquidhydrocarbons boiling above the gasoline range.

The present invention relates to the improvement of catalyst performancein hydrocarbon conversion where metal poisoning occurs. Althoughreferred to as "metals", these catalyst contaminants may be present inthe hydrocarbon feed in the form of free metals or relativelynon-volatile metal compounds. It is, therefore, to be understood thatthe term "metal" as used herein refers to either form. Various petroleumstocks have been known to contain at least traces of many metals. Forexample, Middle Eastern crudes contain relatively high amounts ofseveral metal components, while Venezuelan crudes are noteworthy fortheir vanadium content and are relatively low in other contaminatingmetals such as nickel. In addition to metals naturally present inpetroleum stocks, including some iron, petroleum stocks also have atendency to pick up tramp iron from transportation, storage andprocessing equipment. Most of these metals, when present in a stock,deposit in a relatively non-volatile form on the catalyst during theconversion processes so that regeneration of the catalyst to removedeposited coke does not also remove these contaminants.

Typical crudes which are contaminated with metals and some averageamounts of metal are: North slope, 11 ppm nickel, 33 ppm vanadium;Lagomedio (Venezuelan), 12 ppm nickel, 116 vanadium; light Iranian, 16ppm nickel, 44 ppm vanadium; heavy Iranian, 30 ppm nickel, 22 ppmvanadium. In general, a crude oil can contain from about 5 to 500 ppmnickel and from about 5 to 1500 ppm vanadium. Moreover, since the metalstend to remain behind during processing, the bottoms of typical feedswill have an amount of metals two, three, four times or more than theoriginal crude. For example, reduced crude or residual stocks can havevanadium levels as high as 1000-2000 ppm. Typical residual stocks andtheir vanadium level include: Sag River atmospheric residuum, 48 ppmvanadium; heavy Iranian atmospheric residuum, 289 ppm vanadium; Canadiantar sand bitumen, 299 ppm vanadium; Tia Juana Vacuum residuum, 570 ppmvanadium; and Orinoco Heavy Crude, 1200 ppm vanadium. The higher themetal level in the feed, the more quickly a given catalyst will bepoisoned and consequently the more often or more effective thedemetallization of that catalyst must be.

Of the various metals which are to be found in representativehydrocarbon feedstocks some, like the alkali metals, only deactivate thecatalyst without changing the product distribution; therefore, theymight be considered true poisons. Others such as iron, nickel, vanadiumand copper markedly alter the selectivity and activity of crackingreactions if allowed to accumulate on the catalyst and, since theyaffect process performance, are also referred to as "poisons". Apoisoned catalyst with these metals generally produces a higher yield ofcoke and hydrogen at the expense of desired products, such as gasolineand butanes. For instance, U.S. Pat. No. 3,147,228 reports that it hasbeen shown that the yield of butanes, butylenes and gasoline, based onconverting 60 volume percent of cracking feed to lighter materials andcoke dropped from 58.5 to 49.6 volume percent when the amount of nickelon the catalyst increased from 55 ppm to 645 ppm and the amount ofvanadium increased from 145 ppm to 1480 ppm in a fluid catalyticcracking of a feedstock containing some metal contaminated stocks. Sincemany cracking units are limited by coke burning or gas handlingfacilities, increased coke or gas yields require a reduction inconversion or throughput to stay within the unit capacity.

Many patents have issued discussing various approaches to removingmetals from hydrocarbon conversion catalysts and then returning thecatalyst to hydrocarbon conversion service. Certain of these patentsinvolved chlorinating metal contaminated alumina, silica-alumina andsilica catalysts at elevated temperatures. See, for example, U.S. Pat.Nos. 3,150,104; 3,122,510; 3,219,586; and 3,182,025. In each of thesepatents, the chlorinated catalyst is preferably cooled prior to contactwith a liquid aqueous wash to avoid the use of excessive pressures tomaintain the liquid phase. These patents do not disclose that suchcooling affects the catalytic activity of such oxide-based catalysts. Incertain instances, prior patents have taught the use of liquid aqueouscompositions containing ammonium ion to at least partially neutralizethe chlorine and/or hydrogen chloride which exists with the chlorinatedcatalyst.

In the more recent past, other demetallization processes have beensuggested which do not primarily involve chlorinating of the catalyst.See, for example, U.S. Pat. Nos. 4,101,444; 4,163,709; 4,163,710;4,243,550 and related patents. These newer processes seek to effectivelydemetallize the newer, zeolite-containing catalysts while eliminatingthe use and handling of chlorinating agents and chlorinated catalystwhich are often corrosive, particularly at elevated temperatures. Theserelatively less severe demetallization processes were also thought to beless likely to detrimentally affect the relatively fragilezeolite-containing catalysts. However, these "non-chlorinating"processes have been found in a number of situations to be not aseffective in catalyst demetallization as processing schemes involvingcatalyst chlorination. However, because of the corrosion and catalyst,particularly zeolite-containing catalyst, destruction problems perceivedto exist, catalyst chlorination as a demetallization technique hasreceived less and less consideration for commercialization. Clearly, itwould be advantageous to provide an improved catalyst demetallizationprocess involving catalyst chlorination.

Therefore, one object of the present invention is to provide an improvedprocess for demetallizing a metal contaminated, hydrocarbon conversioncatalyst.

Another object of the present invention is to provide an improvedhydrocarbon conversion process utilizing as at least a portion of thecatalyst a demetallized catalyst. Other objects and advantages of thepresent invention will become apparent hereinafter.

An improved process for demetallizing a catalyst contaminated with atleast one contaminant metal while promoting hydrocarbon conversion of afeedstock containing the contaminant metal or metals has beendiscovered. The process includes the steps of contacting the catalyst atelevated temperature with at least one chlorine-containing component toform a chlorinated catalyst and contacting the chlorinated catalyst withat least one liquid aqueous composition to produce a demetallizedcatalyst having a reduced content of the contaminant metal or metals. Inone broad aspect, the present improvement comprises utilizing a catalystcomprising at least one synthetic crystalline material, i.e., zeolite,capable of promoting the hydrocarbon conversion; and cooling thechlorinated catalyst prior to the first contacting of the chlorinatedcatalyst with the liquid aqueous composition, thereby forming ademetallized catalyst with improved hydrocarbon conversion catalyticactivity, relative to a demetallized catalyst formed without suchcooling. In another broad embodiment, the present improvement comprisesutilizing a catalyst comprising at least one zeolite capable ofpromoting the hydrocarbon conversion and contacting the chlorinatedcatalyst with a liquid aqueous composition substantially free ofammonium ions, thereby forming a demetallized catalyst with improvedhydrocarbon conversion catalytic activity, relative to a demetallizedcatalyst first contacted with an ammonium ion-containing liquid aqueouscomposition.

The present invention provides substantial and surprising benefits. Byproperly choosing the chlorinated catalyst temperature and/or chemicalmake-up of the first liquid aqueous composition to contact thechlorinated catalyst, a demetallized catalyst having surprisinglyimproved catalytic activity is obtained. Not only is the catalysteffectively demetallized, chlorine-related corrosion reduced and/orammonia or ammonium salt cost eliminated, the catalytic activity ofsynthetic crystalline material-containing hydrocarbon conversioncatalysts is actually increased by practicing the present improveddemetallization processes.

In another embodiment, the invention is directed to a hydrocarbonconversion process employing a catalyst to promote the conversion of asubstantially hydrocarbon feedstock. In this embodiment, the presentimprovement comprises at least one, preferably both, of the following:(1) subjecting at least a portion of the catalyst to the presentdemetallization process; and (2) employing the demetallized catalystfrom the present demetallization process as at least a portion of thecatalyst in the hydrocarbon conversion process.

The presently useful cooling step may be performed in any suitablemanner and in any suitable equipment. It is preferred that thechlorinated catalyst be kept substantially anhydrous during thiscooling. In one embodiment, the cooling occurs by contacting therelatively high temperature chlorinated catalyst with a lowertemperature gaseous composition, preferably a substantially inertgaseous composition such as nitrogen, combustion flue gases, carbondioxide, argon, the other inert gases and the like. In addition toproviding for at least a portion of the cooling to the chlorinatedcatalyst, this gaseous composition contacting preferably acts to reducethe chlorine (or chloride) content of the chlorinated catalyst and/orreduces the content of at least one of the contaminant metals, inparticular vanadium, from the chlorinated catalyst, e.g., by "sweeping"away volatile metal chlorides which are formed during catalystchlorination. It should be noted that the gaseouscomposition/chlorinated catalyst contacting may occur to provide for oneor both of reducing chlorine content and/or metal content withoutproviding at least a portion of the cooling. Thus, for example, thepurging gas or gases may be contacted with the chlorinated catalyst,e.g., in the chlorinating reaction zone, at or about substantially thesame temperature, or higher, at which the chlorination occurred.Reducing the chlorine content during such purging gas contacting ispreferred since the pH of the first mixture of catalyst/liquid aqueouscomposition is less acid and harmful dissolution of alumina, if presentin the catalyst is inhibited.

The cooling may occur in a separate heat exchanger, e.g., conventionalcatalyst cooler, in which heat from the chlorinated catalyst isindirectly provided to a cooling medium, such as a liquid or gaseousmedium. It is preferred that the hot chlorinated catalyst not contactany liquid medium prior to being cooled as described herein. The degreeof cooling may vary widely, provided that such cooling provides ademetallized catalyst with improved hydrocarbon conversion catalyticactivity. Preferably, this cooling reduces the temperature of thechlorinated catalyst by at least about 50 degrees F. In one particularembodiment, the cooling reduces the temperature of the chlorinatedcatalyst to a temperature in the range of about 50 degrees F. to about250 degrees F., more preferably about 60 degrees F. to about 150 degreesF.

The composition of the hydrocarbon conversion catalysts useful in thepresent invention may vary widely provided that the catalyst contains atleast one synthetic crystalline material in an amount effective topromote the desired hydrocarbon conversion at hydrocarbon conversioncondition. Materials known as zeolites or molecular sieves are onepreferred class of synthetic crystalline materials. Useful zeolitesinclude not only synthetic zeolites, but also naturally occurringzeolites the chemical make-up of which is modified or changed to enhanceone or more of the catalytic properties of the naturally occurringzeolite.

When the desired hydrocarbon conversion involves one or more ofhydrocarbon cracking (preferably in the substantial absence of addedfree molecular hydrogen), disproportionation, isomerization,hydrocracking, reforming, dehydrocyclization, polymerization, alkylationand dealkylation, synthetic crystalline materials aluminosilicates,SAPO. TAPO. MeAPO, AlPO, ZSM-series, LZ-Z10, LZ-10, USY and the like.Certain of these synthetic crystalline materials are discussed in U.S.Pat. Nos. 4,310,440; 4,440,871; 4,500,651; and 4,503,023, thespecification of each of which patents is incorporated by referenceherein. Of these, catalysts which include a catalytically effectiveamount of USY are particularly preferred.

Compositions of the catalysts which are particularly useful in thepresent invention are those in which the synthetic crystalline materialsis incorporated in an amount effective to promote the desiredhydrocarbon conversion, e.g., a catalytically effective amount, into aporous matrix which comprises, for example, amorphous material which mayor may not be itself capable of promoting such hydrocarbon conversion.Included among such matrix materials are clays and amorphouscompositions of alumina, silica, silica-alumina, magnesia, zirconia,mixtures of these and the like. The synthetic crystalline material ispreferably incorporated into the matrix material in amounts within therange of about 1% to about 75%, more preferably about 2% to about 50%,by weight of the total catalyst. The preparation ofcrystalline-amorphous matrix catalytic materials is described in U.S.Pat. Nos. 3,140,253 and Re.27,639. Catalytically active syntheticcrystalline materials which are formed during and/or as part of themethods of manufacturing the catalyst are within the scope of thepresent invention.

The catalysts useful in the catalytic hydrocarbon cracking embodiment ofthe present invention may be any conventional catalyst capable ofpromoting hydrocarbon cracking at the conditions present in the reactionzone, i.e., hydrocarbon cracking conditions and containing at least oneof the above-noted synthetic crystalline materials. Similarly, thecatalytic activity of such solid particles is restored at the conditionspresent in a conventional cracking unit regeneration zone. Typical amongthese conventional catalysts are those which comprise alumina, silicaand/or silica-alumina and at least one synthetic crystalline material,e.g., aluminosilicate, having pore diameters of about 8 angstroms toabout 15 angstroms and mixtures thereof. When the catalysts to be usedin the hydrocarbon cracking embodiment of the present invention containcrystalline aluminosilicate, the crystalline aluminosilicate may includeminor amounts of conventional metal promoters such as the rare earthmetals, in particular cerium.

This invention makes use of chlorination, preferably vapor phasechlorination, at moderately elevated temperatures up to about 700degrees F. or even up to about 900 degrees F. or 1000 degrees F.,wherein the catalyst composition and structure is not materially harmedby the treatment and a substantial amount, preferably at least about 30%and more preferably at least about 50%, of the poisoning metals contentis converted to chlorides. The chlorination preferably takes place at atemperature of at least about 300 degrees F., more preferably about 550degrees to 650 degrees F. The chlorination, even when conducted in thelower temperature ranges, e.g., below about 550 degrees F., preferablyserves simultaneously to remove, by volatilization, vanadium chloridessuch as vanadium oxychloride and/or vanadium tetrachloride and/or ironchloride formed by chlorination. When volatilization of these compoundsis not performed or not completed during chlorination, the chlorinationmay be followed by a purge with an inert gas such as nitrogen or fluegas in these higher temperature ranges, that is, about 550 degrees F. toabout 700 degrees F. or about 1000 degrees F. for volatilization ofthese compounds.

The chlorinating agent or mixture is preferably substantially anhydrous,that is, if changed to the liquid state no separate aqueous phase wouldbe observed. As the amount of water in the chlorinating agent increases,additional time and/or chlorinating agent may be required to obtain agiven amount of metal removal. This inhibiting effect is also evidentwhen water is present in the catalyst so that it is preferred that thecatalyst contain less than about 1% or about 2% volatile matter, thatis, matter which is removable by heating to 1000 degrees C. A pressureof about 0 to about 100 or more psig., preferably about 0 to about 15psig. may be maintained during chlorination, the contacting usuallylasting for at least about five minutes, preferably about 15 minutes toabout 2 hours, but shorter or longer reaction periods may be possible orneeded.

The chlorinating mixture preferably contains a chlorinating agent and agaseous inert diluent. The chlorinating agent may be a vaporizablecovalent compound of chlorine with carbon or sulfur. The carboncompounds of chlorine which may be employed are generally thechlorine-substituted light hydrocarbons which may be introduced to thechlorination reactor as such or may be produced during the chlorinationfrom a mixture of a chlorine gas with low molecular weight hydrocarbons.Preferably the carbon compound of chlorine employed is carbontetrachloride. Useful inorganic sulfur-containing compounds include thevolatizable sulfur chlorides, viz. sulfur monochloride, S₂ Cl₂, sulfurdichloride, SCl₂, thionyl chloride, SOCl₂ and sulfuryl chloride, SO₂ Cl₂

The gaseous inert diluent, the other component of one preferredchlorinating mixture, may advantageously be nitrogen or any other gasinert under the reaction conditions. However, it is preferable to avoidthe use of inert gases containing hydrocarbons, even in small amounts.It has been found that the addition of a diluent such as nitrogen may beeffective in reducing the amount of the chlorinating agent used foreffective conversion of, for instance, vanadium to its volatilechlorides.

It has also been found that a chlorinating gas comprising molecularchlorine, hydrogen chloride and mixtures thereof, particularly incombination with one or more of the covalent chlorinating agentsdescribed above, may advantageously be employed as at least part of thechlorinating agent. The covalent chlorinating agent may be provided inlesser amounts when molecular chlorine or HCl is present, while stillresulting in substantial effective conversion of contaminating metals totheir chlorides at the moderate temperatures of the process. Molecularchlorine and HCl are considerably less expensive than, say, carbontetrachloride or other agents and thus a combination of the agent andmolecular chlorine or HCl is economically attractive.

If employed, the vaporizable covalent carbon or sulfur compounds ofchlorine are generally used in the amount of about 0.5-50 percent,preferably 1-10 percent, based on the weight of the catalyst, for goodmetals removal. The amount of the agent may vary, however, dependingupon the manipulative aspects of the chlorination step, for example, abatch treatment may sometimes require more agent than a continuoustreatment for the same degree of effectiveness and results.

When molecular chlorine or HCl are employed as at least part of thechlorinating agent they are supplied in amounts preferably in the rangeof about 0.5% to about 150%, more preferably about 2% to about 35% basedon the weight of the catalyst. The gaseous inert diluent advantageouslyis used in amounts of about 1% to about 25%, more preferably about 2% toabout 15%, based on the weight of the catalyst treated.

The process of this invention produces significantly greater removal ofvanadium when, upon removal of the vanadium-poisoned catalyst from thehydrocarbon conversion reactor, it is regenerated and given a treatmentat elevated temperatures with molecular oxygen-containing gas beforechlorination.

Regeneration of a catalyst to remove carbon is a relatively quickprocedure in most commercial catalytic conversion operations. Forexample, in a typical fluidized cracking unit, a portion of catalyst iscontinually being removed from the reactor and sent to the regeneratorfor contact with air at about 950 degrees F. to about 1400 degrees F.,more usually about 1000 degrees F. to about 1350 degrees F. Combustionof coke from the catalyst is rapid, and for reasons of economy onlyenough air is used to supply the needed oxygen. Average residence timefor a portion of catalyst in the regenerator may be on the order ofabout a few minutes, e.g., about 5 minutes to about 10 minutes, and theoxygen content of the effluent gases from the regenerator is desirablyless than about 1/2% by volume. When later oxygen treatment is employedin this invention, the regeneration of the catalyst is generallyregulated to give a carbon content of less than about 0.5% by weight.

Treatment of the regenerated catalyst with molecular oxygen-containinggas to increase vanadium removal is preferably conducted at temperaturespreferably above the temperature present in the catalyst regenerationzone, more preferably in the range of about 1000 degrees to 1800 degreesF. but below a temperature where the catalyst undergoes any substantialdeleterious change in its physical or chemical characteristics. Thecatalyst is preferably in a substantially carbon-free condition duringthis high temperature treatment. If any significant amount of carbon ispresent in the catalyst at the start of this high-temperature treatment,the oxygen contact is preferably that continued after carbon removal. Inany event, after carbon removal, the oxygen treatment of the essentiallycarbon-free catalyst is prefeably at least long enough to provide asubstantial amount of vanadium in its highest valence state.

The treatment of the catalyst with molecular oxygen-containing gas priorto the chlorination is preferably performed at a temperature at leastabout 50 degrees F. higher than the regeneration temperature. Theduration of the oxygen treatment and the amount of vanadium prepared bythe treatment for subsequent removal is dependent, for example, upon thetemeperature and the characteristics of the equipment used. The lengthof the oxygen treatment preferably is in the range of about a quarter ofan hour to about four hours or more. The oxygen-containing gas used inthe treatment preferably contains molecular oxygen and there is littlesignificant consumption of oxygen in this treatment. The gas may beoxygen, or a mixture of oxygen with inert gas, such as air oroxygen-enriched air. The partial pressure of oxygen in the treating gasmay range widely, for example, from about 0.1 to 30 atmospheres. Thefactors of time, partial pressure and extent of vanadium stabilizationmay be chosen with a view to the most economically feasible set ofconditions. It is preferred to continue the oxygen treatment for atleast about 15 or 30 minutes with a gas containing at least about 1% byvolume, preferably at least about 10% by volume oxygen.

The chlorination method of the invention is of value, not only in theremoval of vanadium from the catalyst, but also in putting nickelpoisons into a form soluble in an aqueous composition. Also thechlorinating method may be used as a supplement, primarily for vanadiumremoval, to a complete processing scheme for nickel removal in whichchlorination does not play a significant part. For example, sulfiding ofthe poisoned catalyst has been found to be advantageous for nickel andperhaps vanadium contaminant removal by subsequent chlorination andwater washing or by other subsequent treatments which put nickel into adispersible form, or which dissolve or disperse nickel directly from thesulfided catalyst.

The sulfiding step can be performed by contacting the poisoned catalystwith elemental sulfur vapors, or more conveniently by contacting thepoisoned catalyst with a volatile sulfide, such as H₂ S, CS₂ or amercaptan. The contact with the sulfur-containing vapor can be performedat an elevated temperature generally in the range of about 500 degreesF. to about 1500 degrees F., preferably about 800 degrees F. to about1300 degrees F. Other treating conditions can include asulfur-containing vapor partial pressure of about 0.1 to about 30atmospheres or more, preferably about 0.5 to about 25 atmospheres.Hydrogen sulfide is a preferred sulfiding agent. Pressures belowatmospheric can be obtained either by using a partial vacuum or bydiluting the vapor with gas such as nitrogen or hydrogen. The time ofcontact may vary on the basis of the temperature and pressure chosen andother factors such as the amount of metal to be removed. The sulfidingmay run, for instance, at least about 5 or 10 minutes up to about 20hours or more depending on the sulfiding conditions and the severity ofthe catalyst poisoning. Temperatures of about 900 degrees F. to about1200 degrees F. and pressures approximating 1 atmosphere or less arepreferred for sulfiding and this treatment often continues for at leastabout 1 to 2 hours but the time, of course, can depend upon the mannerof contacting the catalyst and sulfiding agent and the nature of thetreating system, e.g., batch or continuous, as well as the rate ofdiffusion within the catalyst. The sulfiding step performs the functionnot only of supplying a sulfur-containing metal compound which may beeasily converted to chloride form but also appears to concentrate somemetal poisons, especially nickel, at the surface of the catalystparticle.

After chlorination and preferably after at least partial vaporization ofvanadium chlorides, and after the chlorinated catalyst is cooled, asdescribed, the catalyst is washed in a liquid aqueous composition,preferably substantially free of ammonium ions, to remove at least aportion of the contaminant metal, for instance nickel chlorides.

The water used is sometimes distilled or deionized prior to contact withthe chlorinated catalyst. However, the aqueous medium can containextraneous ingredients in trace amounts, so long as the medium isaqueous-based and the extraneous ingredients do not interfere withdemetallization or adversely affect the properties of the catalyst.Temperatures of about 150 degrees F. to the boiling point of water arehelpful in increasing the solubility of the metal chlorides.Temperatures above 212 degrees F. and elevated pressures may be used butthe results do not seem to justify the added equipment. The aqueousliquid is preferably acid and a weakly acid condition may be obtained bythe chlorides generally present in a chlorinated catalyst which has notbeen purged too severely.

The initial liquid aqueous composition may be a reductive wash medium,which is preferably followed by an oxidative wash. These washes my begiven alternately or several reductive washes may be followed by severaloxidative washes. When alternating washes are used, the final wash ispreferably an oxidative wash to leave the catalyst in the best form forhydrocarbon conversion, e.g., cracking. As used herein, "reductive" washrefers to a wash with an aqueous solution containing a reducing agent oran agent which may give up electrons. Similarly, "oxidative" wash refersto a wash with an aqueous solution containing an oxidizing agent or anagent which may accept electrons. Moreover, "wash" refers to a treatmentwith the solution which may be accomplished by contacting the catalystwith the wash solution for a time sufficient to cause an interactionbetween the solution and catalyst thereby removing at least a portion ofthe metal poison. The contacting may be a batch operation, asemi-continuous operation or a continuous operation. Thus, a "wash" mayinclude merely stirring in a batch vessel or a complex series of countercurrent contactors or continuous contactors.

A preferred reductive wash medium comprises a solution of sulfur dioxideor compounds capable of producing sulfur dioxide such as sulfides andbisulfites in an acidic aqueous medium. Other reducing agents which maybe used include hydrogen, carbon monoxide, hydrogen sulfide oxalic acidor salts thereof, hydrazine and hydrazine derivatives, borane, diborane,borohydrides, metallic aluminum hydrides, sulfites, thiosulfites,dithionites, poly-thionites and the like. A reductive wash with one ormore of the preferred reducing agents do not require a subsequentoxidative wash. The preferred reducing agents include, in addition tosulfur dioxide, hydrogen, carbon monoxide, hydrogen sulfide, hydrazine,and hydrazine derivatives, borane, diborane, borohydrides, metallicaluminum hydrides, sulfites, thiosulfites, dithionites, hydrothionites,polythionites and mixtures thereof. Sulfur dioxide is particularlypreferred since it provides sufficient temporary acidity without riskingsubstantial alumina removal from the catalyst, it provides sufficientreducing power and it produces stable anions containing sulfur andoxygen to keep the removed metals in a soluble form. Reductive washeswith sulfur dioxide are preferably effected at conditions to inhibitoxidation of the SO₂, e.g., in the absence of oxygen, thereby renderingan oxidative system instead of the desired reductive system. By way ofexample of a preferred reductive wash, an aqueous solution saturatedwith sulfur dioxide to form a sulfur oxide hydrate (i.e., SO₂. xH₂ O) isprepared at about 0 degrees C. to about 20 degrees C. preferably about 5degrees C. to about 15 degrees C., by bubbling SO₂ through water. Anaqueous, e.g., about 10-%40% and preferably about 15-25% by weight,catalyst slurry in water is prepared and heated to a temperature ofabout 60 degrees C. to about 95 degrees C., preferably about 65 degreesC. to about 80 degrees C. The SO₂ saturated solution is then added tothe catalyst slurry in an amount sufficient to give an initial pH of thesystem in the range of about 2.0 to about 3.5 and preferably about 2.5to about 3.0. Preferably, about 0.1 to about 10 volumes of S₂ saturatedsolution per volume of catalyst are used during the wash. After thecontacting has occurred for about 0.5-10 minutes, preferably about 1-5minutes, preferably under an inert atmosphere, the demetallized catalystcan be separated, e.g., by filtration or decanting. Long contact tixes,i.e., in excess of about 10 minutes, are preferably avoided to minimizemetals redisposition on the catalyst and to avoid oxidation of the SO₂should the wash be effected in a manner where air and oxygen are notintentionally excluded. This reductive wash step can be followed by awater wash.

As indicated, the reductive wash preferably is followed by an oxidativewash. A preferred oxidative wash medium comprises a solution of hydrogenperoxide in water. Other oxidizing agents which may be used include air,oxygen, ozone, perchlorates, organic hydroperoxides, organic peroxides,organic peracids, inorganic peroxyacids such a peroxymonosulfuric andperoxydisulfuric acid, singlet oxygen, NO₂, N₂ O₄, N₂ O₃, superoxidesand the like. Typical examples of organic oxidants are hydroxlheptylperoxides, cyclohexanone peroxide, tertiary butyl peracetate,di-tertiary butyl diperphthalate, tertiary butyl perbenzoate, methylethyl ketone peroxide, dicumyl peroxide, tertiary butyl hydroperoxide,di-tertiary butyl peroxide, p-methyl benzene hydroperoxide, pinanehydroperoxide, 2,5-dimethylhexane-2, 5-dihydroperoxide, cumenehydroperoxide and the like; as well as organic peracids such asperformic acid, peracetic acid, trichlorperacetic acid, perchloric acid,periodic acid, perbenzoic acid, perphthalic acid and the like includingsalts thereof. Ambient oxidative wash temperatures can be used, buttemperatures of about 150 degrees F. to the boiling point of the aqueoussolution in combination with agitation are helpful in increasingdispersibility or removability of the metal poisons. Preferredtemperatures are about 65 degrees to about 95 degrees C. Pressure aboveatmospheric may be used but the results usually do not justify theadditional equipment. Contact times similar to the contact times for thereductive wash such as from about several seconds to about half an hourare usually sufficient for poisoning metal removal.

As indicated, preferably the SO₂ reductive wash is followed by ahydrogen peroxide-water oxidative wash. The hydrogen peroxide solutionpreferably containing about 2 to 30 weight % hydrogen peroxide, can beadded to an aqueous catalyst slurry as described earlier at about 65degrees C. to about 95 degrees C., preferably 60 degrees C. to about 85degrees C. and allowed to react for a time sufficient to solubilize atleast a portion of the vanadium. Preferred wash times are about 1- 5minutes. A concentration of H₂ O₂ in the range of about 5-501b.,preferably about 10-20 lb. of H₂ O₂ /ton of catalyst is preferably used.Additional oxidative washes can be used to ensure efficient removal ofmetal and the restoration of catalytic properties. In addition, theoxidative washing can be carried out either in the presence of orabsence of a mineral acid such as HCl, HNO₃ of H₂ SO₄. Preferably, thepH of the oxidative wash medium is about 2 to about 6. Alternatingcatalyst washing using reductive and oxidative solutions can be used. Ifalternative washes are used, it is preferred that the last wash be anoxidative wash.

After the catalyst is washed, the catalyst slurry can be filtered togive a cake. The cake may be reslurried one or more times with water orrinsed in other ways, such as, for example, by a water wash of thefilter cake.

After the washing and rinsing treatment which may be used in thecatalyst demetallization procedure, the catalyst is transferred to ahydrocarbon conversion system, for instance, to a catalyst regenerator.The catalyst may be returned as a slurry in the final aqueous washmedium, or it may be desirable first to dry the catalyst filter cake orfilter cake slurry at, for example, about 215 degrees F. to about 320degrees F., under a vacuum. Also, prior to reusing the catalyst in theconversion operation it can be calcined, for example, at temperaturesusually in the range of about 700 degrees F. to about 1300 degrees F.Preferably, the demetallized catalyst is not calcined at a temperaturehigher than the temperature present during catalyst regeneration, e.g.,in the catalyst regeneration zone, prior to rinsing the catalyst in thehycrocarbon conversion operation. Such high temperature calcination hasbeen found to reduce the catalytic effectiveness of the demetallizedcatatlyst. The catalyst may be slurried with hydrocarbons and added backto the reactor vessel, if desired.

If desired, additional metals removal may be obtained by repeating thedemetallization sequence or using other known treatment processes. Inertgases frequently may be employed after contact with reactive vapors toremove any of these vapors entrained in the catalyst or to purge thecatalyst of reaction products.

The catalyst to be treated may be removed from the hydrocarbonconversion system--that is, the stream of catalyst which, in mostconventional procedures, is cycled between conversion and regeneratingoperations--before the poison content reaches about 100,000 ppm., thepoisoning metals, e.g., nickel, vanadium, iron, copper and mixturesthereof, being calculated as elemental metals.

The amount of nickel, vanadium, iron and/or copper removed in practicingthe procedures outlined or the proportions of each may be varied byproper choice of treating conditions. It may prove necessary, in thecase of very severely poisoned catalyst, to repeat the treatment toreduce the metals to an acceptable level, perhaps with variations whenone metal is greatly in excess. A further significant advantage of theprocess lies in the fact that the overall metals removal operation, evenif repeated, does not unduly deleteriously affect the activity,selectivity, pore structure and other desirable characteristics of thecatalyst. Any given step in the demetallization treatment is usuallycontinued for a time sufficient to effect a meaningful conversion orremoval of poisoning metal and ultimately results in a substantialincrease in metals removal compared with that which would have beenremoved if the particular step had not been performed. Preferably, thepresent catalyst demetallization process will provide greater than abouta 50 weight % reduction in nickel, about 50 weight % reduction invanadium and about 30 weight % reduction in iron. Such processingpreferably provides about 70-90 weight % reduction in nickel, about50-80 weight % reduction in vanadium and about 30-75 weight reduction iniron when the catalyst initially contains as much as about 0.1 to 0.5weight % nickel, about 0.3 to 1.0 weight % vanadium and about 0.2 to 1.2weight % of iron.

In this invention the substantially hydrocarbon oils utilized asfeedstock for a given conversion process may be of any desired typenormally utilized in such hydrocarbon conversion operations. Thefeedstock may contain nickel, iron and/or vanadium as well as othermetals. The catalyst may be used to promote the desired hydrocarbonconversion by employing at least one fixed bed, moving bed or fluidizedbed (dense or dilute phase) of such catalyst. Bottoms from hydrocarbonprocesses, (i.e., reduced crude and residuum stocks) are particularlyhighly contaminated with these metals and therefore rapidly poisoncatalysts used in converting bottoms to more valuable products. Forexample, a bottom may contain about 100-1500 ppm Ni, about 100-2500 ppmV and about 100-3000 ppm Fe. For typical operations, the catalyticcracking of the substantially hydrocarbon feed would often result in aconversion of about 10 to 80% by volume of the feedstock into lowerboiling, more valuable products.

The present invention is particularly suitable for demetallizingcatalysts utilized in the catalytic cracking of reduced, or topped crudeoils to more valuable products such as illustrated in U.S. Pat. Nos.3,092,568 and 3,164,542. The teachings of which are incorporated byreference herein. Similarly, this invention is applicable to processingshale oils, tar sands oil, coal oils and the like where metalcontamination of the processing, e.g., cracking catalyst, can occur.

The following non-limiting examples illustrate certain aspects of thepresent invention.

EXAMPLES 1 to 3

A mass of commercial equibrium fluid catalytic cracking catalyst wasobtained for testing. This catalyst was originally manufactured byFiltrol and contained a catalytically effective amount of USY syntheticzeolite. The catalyst had been used in a commercial fluid bed catalyticcracking operation and included amounts of vanadium, iron and nickelfrom the catalytic cracking hydrocarbon feedstock which becameassociated with the catalyst when the catalyst was in the crackingreaction zone.

A portion of this catalyst was subjected to the following procedure.

A two inch i.d. by eighteen inch long quartz vessel fitted with a coarsequartz frit was used as a reactor vessel. One inch i.d. by ten inch longextensions were positioned at either end of this reactor vessel andterminated in ball joints which allowed quick disconnecting of theentire assembly, if desired, for example, for aqueous quenching of thecatalyst after demetallization. Heat to the fluid bed reactor vessel wassupplied by a Lindberg Model 54442-D furnace. Heat tracing of entry andexit gases was effected by external heat tape wrapping.

One pound of the above-noted catalyst was charged to this reactor vesseland fluidized with bottled air while heating to 1350 degrees F. Whenslumped the bed was ten inches high and when fluidized the bed wasfourteen inches high. Approximately two hours were needed for heating tooperating temperature, including a fifteen minute period when the gaslines and the fluid bed were flushed with nitrogen before introducing H₂S.

After this nitrogen flush, the catalyst bed was fluidized with 100% H₂ Sfor four hours. Following this sulfiding step, the reactor vessel andcontents were cooled to 650 degrees F. under nitrogen fluidization. Thecatalyst bed was then fluidized with 100% chlorine gas for 90 minutes at650 degrees F. Following the chlorination, the reactor was flushed withnitrogen for fifteen minutes while maintaining a temperature of about650 degrees F. This nitrogen purge removed some chlorine from the voidspace in the catalyst bed and some volatile vanadium, and ironchlorine-containing components.

Half of the hot chlorinated catalyst was contacted with a liquid waterwash. The other half of the chlorinated catalyst was cooled to ambienttemperature, i.e., about 70 degrees F., before being contacted withabout 900 ml. of a liquid water wash. In both instances, thecatalyst/water slurries were filtered on Buchner funnels, washed with athree fold excess of water, reslurried at 4/1 water to catalyst ratio,refiltered, rewashed, and oven dried at 230 degrees F. overnight. Eachof these catalyst samples included reduced amounts of metal, inparticular vanadium and nickel, relative to the original, untreatedcatalyst.

The original, untreated catalyst, and the two demetallized catalystswere each tested for catalytic activity using the Micro Activity test(ASTM D 3907-80). Results of these tests were as follows.

    ______________________________________                                        EXAMPLE                                                                                  1          2          3                                                       Original   Hot Washed Cool Washed                                             Untreated  Demetallized                                                                             Demetallized                                            Catalyst.sup.(2)                                                                         Catalyst   Catalyst                                     Component.sup.(1)                                                                        55.3       58.5       61.2                                         MAT NUMBER Wt. %      Wt. %      Wt. %                                        ______________________________________                                        Gas         2.81       2.81       3.10                                        Gasoline   48.97      51.10      53.52                                        Light Cycle Oil                                                                          30.77      28.18      26.72                                        Decant Oil 13.90      13.36      12.11                                        Coke        3.56       4.56       4.54                                        ______________________________________                                         .sup.(1) Component distillation cuts were: gas, to C.sub.4 ; gasoline,        C.sub.4 to 421 degrees F.; light cycle oil, 421 degrees F. to 651 degrees     F.; decant oil, 651 degrees F. plus.                                          .sup.(2) Average of two Micro Activity Tests                             

These results clearly show that cooling a chlorinated zeolite-containingcatalyst before initial water contacting/washing provides improvedcatalytic activity. For example, the MAT number and the yield ofvaluable gasoline are substantially increased in the ambient cooledcatalyst relative to the original, untreated catalyst and the hotquenched demetallized catalyst.

EXAMPLES 4 to 6

A second mass of commercial equibrium fluid catalytic cracking catalystwas obtained for testing. This catalyst was commercially manufacturedand contained a catalytically effective amount of a combination of USYand rare earth metal exchanged Y synthetic zeolite. The catalyst hadbeen used in a commercial fluid bed catalytic cracking operation andincluded amounts of vanadium, iron and nickel from the catalyticcracking hydrocarbcon feedstock which became associated with thecatalyst when the catalyst was in the cracking reaction zone.

One pound of this catalyst was treated in the reaction system describedin Examples 1 to 3 by sulfidation and chlorination as described inExamples 1 to 3 except the sulfiding occurred for two hours and thechlorination for one hour.

Following the one hour chlorination, the reactor vessel was flushed withnitrogen for 15 minutes, the ball joint extensions were disconnected andthe hot catalyst divided into two one-half pound portions. One portionof the hot catalyst was contacted with about 900 ml. of deionized water,while the other portion of the hot catalyst was contacted with about 900ml. of an aqueous solution of ammonium chloride at pH equal to about 3.

Each of the slurries (resulting from the above-noted contactings) wasfiltered on Buchner funnels, washed with a three-fold excess of water,reslurried at a 4/1 water to catalyst ratio, refiltered, rewashed andoven dried at 230 degrees F. overnight. Each of these catalysts portionsincluded reduced amounts of metal relative to the original, untreatedcatalyst.

The original, untreated catalyst, and the two demetallized catalystswere each tested for catalytic activity using the Micro Activity test(ASTM D 3907-80). Results of these tests were as follows.

    ______________________________________                                        EXAMPLE                                                                                   4          5           6                                                      Original   Washed With Washed                                                 Untreated  Ammonium    With                                                   Catalyst   Ion         Water                                      COMPONENT.sup.(1)                                                                         61.7       60.8        66.4                                       MAT Number  Wt. %      Wt. %       Wt. %                                      ______________________________________                                        Gas          3.33       2.86       3.90                                       Gasoline    55.30      54.89       58.71                                      Light Cycle Oil                                                                           28.23      25.23       23.95                                      Decant Oil  10.05      14.01       9.68                                       Coke         3.09       3.01       3.75                                       ______________________________________                                         .sup.(1) Component Cuts same as in Examples 1 to 3                       

The results clearly show that contacting/washing a chlorinateddemetallized, zeolite-containing catalyst in the substantial absence ofammonium ion provides substantial benefits, e.g., increased MAT numberand yield of valuable gasoline. This is particularly surprising sincemany of the prior patents on demetallizing non-zeolite-containingcatalyst employ ammonium ion to neutralize the chlorinated catalyst.

EXAMPLES 7 and 8

Catalysts demetallized in accordance with procedures described inExamples 3 and 6 are each subjected to a combination ofreductive/oxidative washes.

The reductive wash is performed as follows. The demetallized catalyst isslurried with water to give about a 20 weight % of solids slurry andsufficient sulfur dioxide is added to give an initial pH of 2.0. Thetemperature of the slurry is maintained at about 70 degrees C. for about3 minutes. The catalyst is then filtered and the aqueous sulfur dioxidewash is repeated twice more to give a total of three reductive washes.After an intermediate water wash, the demetallized, reductively washedcatalysts from Example 3 and 6 are subjected to an oxidative wash withan aqueous solution of H₂ O₂. This wash is performed for 3 minutes, at70 degrees C. with a 20 weight % solids slurry utilizing H₂ O₂ in anamount of 10 pounds per ton of catalyst. The catalysts are water washed,filtered and dried.

The demetallized catalysts from Examples 7 and 8, i.e., thereductively/oxidatively washed demetallized catalyst from Examples 3 and6, respectively, have substantially improved catalytic activity relativeto the original untreated catalysts.

EXAMPLES 9 to 12

Catalysts demetallized in accordance with procedures described inExamples 3, 6, 7 and 8 are included in the circulating catalystinventory of a commercial fluid bed catalytic cracking unit processingsubstantially hydrocarbon gas oil. Over a period of time, it isdetermined that all the catalysts perform satisfactorily in thiscommercial operation.

While this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be practiced within the scope of thefollowing claims.

The embodiments of the present invention in which an exclusive propertyor privilege is claimed are as follows:
 1. In a process fordemetallizing a catalyst contaminated with at least one contaminantmetal while promoting hydrocarbon cracking of a feedstock containingsaid contaminating metal, said process including the steps of contactingsaid catalyst at elevated temperature with at least onechlorine-containing component to form a chlorinated catalyst andcontacting said chlorinated catalyst with at least one liquid aqueouscomposition to produce a demetallized catalyst having a reduced contentof said contaminant metal, the improvement comprising utilizing acatalyst comprising at least one synthetic zeolite capable of promotingsaid hydrocarbon cracking; and cooling said chlorinated catalyst priorto the first contacting of said chlorinated catalyst with said liquidaqueous composition, said liquid aqueous composition being substantiallyfree of ammonium ions thereby forming a demetallized catalyst withimproved hydrocarbon cracking catalytic activity.
 2. The process ofclaim 1 wherein said cooling reduces the temperature of said chlorinatedcatalyst by at least about 50 degrees F.
 3. The process of claim 1wherein said cooling reduces the temperature of said chlorinatedcatalyst to a temperature in the range of about 50 degrees F. to about250 degrees F. degrees F.
 4. The process of claim 1 wherein said coolingreduces the temperature of said chlorinated catalyst to a temperature inthe range of about 60 degrees F. to about 150 degrees F.
 5. The processof claim 1 wherein said contaminant metal is selected from the groupconsisting of vanadium, nickel, iron, copper and mixtures thereof. 6.The process of claim 5 wherein said catalyst is contacted with at leastone sulfur-containing component to form a sulfided catalyst prior tobeing contacted with said chlorine-containing component.
 7. The processof claim 1 wherein said demetallized catalyst is further subjected to atleast one reductive wash and at least one oxidative wash.
 8. The processof claim 1 wherein said chlorinated catalyst is contacted with a gaseouscomposition to reduce the chlorine content of said chlorinated catalystprior to the first contacting of said chlorinated catalyst with saidliquid aqueous composition.
 9. In a process for demetallizing a catalystcontaminated with at least one contaminant metal while Promotinghydrocarbon cracking conversion of a feedstock containing saidcontaminant metal, said process including the steps of contacting saidcatalyst at elevated temperature with at least one chlorine-containingcomponent to form a chlorinated catalyst and contacting said chlorinatedcatalyst with at least one liquid aqueous composition to produce ademetallized catalyst having a reduced content of said contaminantmetal, the improvement comprising utilizing a catalyst comprising atleast one synthetic zeolite capable of promoting said hydrocarboncracking; and providing a liquid aqueous composition substantially freeof ammonium ions, thereby forming a demetallized catalyst with improvedhydrocarbon cracking catalytic activity.
 10. The process of claim 9wherein said contaminant metal is selected from the group consisting ofvanadium, nickel, iron, copper and mixtures thereof.
 11. The process ofclaim 9 wherein said catalyst is contacted with at least onesulfur-containing component to form a sulfided catalyst prior to beingcontacted with said chlorine-containing component.
 12. The process ofclaim 10 wherein said catalyst is contacted with at least onesulfur-containing component to form a sulfided catalyst prior to beingcontacted with said chlorine-containing component.
 13. The process ofclaim 9 wherein said chlorinated catalyst is cooled prior to the firstcontacting of said chlorinated catalyst with said liquid aqueouscomposition.
 14. The process of claim 10 wherein said chlorinatedcatalyst is cooled prior to the first contacting of said chlorinatedcatalyst with said liquid aqueous composition.
 15. The process of claim9 wherein said chlorinated catalyst is contacted with a gaseouscomposition to reduce the chlorine content of said chlorinated catalystprior to the first contacting of said chlorinated catalyst with saidliquid aqueous composition.
 16. The process of claim 9 wherein saiddemetallized catalyst is further subjected to at least one reductivewash and at least one oxidative wash.